Open information extraction (OpenIE) is a generic form of relation extraction which can extract any kind of relations with its arguments from free text. Most OpenIE systems use hand-crafted rules or predefined sentence structures to extract entities and relations from sentences. The advantage of such a system is that it can work on texts from any domain. KnowItAll [1]}, TEXTRUNNER [2]}, REVERB [3]}, SRL-IE [4]}, OLLIE [5]}, and RELNOUN [6]} are some examples of OpenIE systems which can extract reliable facts from text.
